The mechanism of oxygen supply to tissue will be studied by using several new biochemical and biophysical techniques. Synthetic green hemoglobins with different oxygen affinities will be used as a new type of reporter molecule to investigate hemoglobin behavior at molecular and cellular levels. A sensitive automatic oxygen-equilibrium apparatus for hemoglobin and red cell suspensions will be used in order to evaluate the efficiency of oxygen transport by hemoglobin. Since the synthetic green hemoglobins have different colors from those of native hemoglobin, myoglobin and other tissue hemoproteins, the oxy-deoxy transition of the hemoglobin can be independently monitored by the difference in absorption changes. The spin-label method will also be used to study the inter- or intramolecular oxygen transport. The spin-labels attached directly to heme provide important information about the conformational change of protein due to oxygen binding or due to subunit-subunit interaction. It is also possible to prepare various hybrid hemoglobins in which only one type of subunit has a marker (green heme or spin-label). Accurate studies of oxygen binding to these hybrid hemoglobins will provide important information about the molecular mechanism of oxygen binding, particularly the mechanism of heme-heme interaction of hemoglobin. This synthetic hemoglobin will also be incorporated into the red cell membrane in order to study the oxygen transport through the red cell membrane. These fundamental studies of hemoglobin will provide a basis for further understanding and treatment of hemoglobinopathies and disorders of oxygen transport.